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| author | Joseph Myers <joseph@codesourcery.com> | 2018-10-17 21:23:40 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2018-10-17 21:23:40 +0000 |
| commit | c2b7ccad93d6361eba91755e8f0c92e97c76e854 (patch) | |
| tree | 3dd1fd49d02f6f6a903578a30d29a3ebba8cdd87 | |
| parent | 26756e57563e7656e756c0451166e5cd56a5a3cf (diff) | |
| download | glibc-c2b7ccad93d6361eba91755e8f0c92e97c76e854.tar.gz glibc-c2b7ccad93d6361eba91755e8f0c92e97c76e854.tar.xz glibc-c2b7ccad93d6361eba91755e8f0c92e97c76e854.zip | |
Do not allow divide-by-zero exception for pow(+/- 0, -Inf).
C99 wrongly specified a divide-by-zero exception for pow(+/- 0, -Inf); C11 made it optional after this was pointed out, and the permission for this exception has been removed in the current C2x draft. This patch makes the glibc pow tests reflect the stricter requirement (which follows the normal IEEE rules that a divide-by-zero exception is for the case of exact infinite results from *finite* operands, not for such results when any operand is infinite). Tested for x86_64 and x86. (If any other pow implementation in glibc, not exercised on those architectures, turns out to fail the stricter test, it should be fixed to avoid the exception in this case.) * math/libm-test-pow.inc (pow_test_data): Do not allow divide-by-zero exception for pow(+/- 0, -Inf).
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | math/libm-test-pow.inc | 9 |
2 files changed, 12 insertions, 2 deletions
diff --git a/ChangeLog b/ChangeLog index 7dea006c16..450732e565 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2018-10-17 Joseph Myers <joseph@codesourcery.com> + + * math/libm-test-pow.inc (pow_test_data): Do not allow + divide-by-zero exception for pow(+/- 0, -Inf). + 2018-10-17 Zack Weinberg <zackw@panix.com> * manual/job.texi (Job Control is Optional): Remove node, as diff --git a/math/libm-test-pow.inc b/math/libm-test-pow.inc index ff20ad2f04..c7b91c1131 100644 --- a/math/libm-test-pow.inc +++ b/math/libm-test-pow.inc @@ -248,8 +248,13 @@ static const struct test_ff_f_data pow_test_data[] = TEST_ff_f (pow, 0, plus_infty, 0, ERRNO_UNCHANGED), TEST_ff_f (pow, minus_zero, plus_infty, 0, ERRNO_UNCHANGED), - TEST_ff_f (pow, 0, minus_infty, plus_infty, DIVIDE_BY_ZERO_EXCEPTION_OK|ERRNO_UNCHANGED), - TEST_ff_f (pow, minus_zero, minus_infty, plus_infty, DIVIDE_BY_ZERO_EXCEPTION_OK|ERRNO_UNCHANGED), + /* C99 erroneously specified a divide-by-zero exception here, + which is not permitted in C2x (C11 specified it as optional). + See <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1515.pdf> + and + <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2271.pdf>. */ + TEST_ff_f (pow, 0, minus_infty, plus_infty, ERRNO_UNCHANGED), + TEST_ff_f (pow, minus_zero, minus_infty, plus_infty, ERRNO_UNCHANGED), /* pow (x, +inf) == +inf for |x| > 1. */ TEST_ff_f (pow, 1.5, plus_infty, plus_infty, ERRNO_UNCHANGED|NO_TEST_INLINE), |